The present invention relates to a tensioning device for the driving spring of an energy store for electrical switches.
Such a device is used, for example, to operate circuit breakers, such as the type VA three-pole vacuum circuitbreaker manufactured by Sachenwerk Aktiengesellschaft, Federal Republic of Germany.
Various configurations are known for tensioning devices of this type. Compared to other step-down gear assemblies with form-locking transmission elements, such as toothed gear and worm drives, they utilize the high efficiency and small dimensions of overrunning clutches. Compared to charging means operating with ratchet wheels and pawls, they have the advantage of operating free of jolts independently of the tooth pitch and thus keep intermittent stresses away from the transmission members.
A tensioning device of this type is disclosed in the Federal Republic of German patent document No. 1,490,720 in which motion is transferred between parallel shafts by way of eccentrics and driving levers which rest against them under spring pressure. The drive motor is here connected with the shaft supporting the eccentric by means of a V-belt drive.
A prior art tensioning device is also shown the Federal Republic of German patent document No. 1,665,936 as an arrangement equipped with two overrunning clutches and associated eccentrics for a switch drive including a spring drum.
Finally, the Federal Republic of Germany patent document No. 3,131,903 discloses an electromotor drive in which the known transmission elements are also employed.
The prior art drives have in common that the axis of the motor and possibly also the axis of a hand crank that can be attached, preferably for emergency operation, lie parallel to the axis of the shaft on which acts the drive spring for the switch. However, for switches installed in small-volume, encapsulated switching systems as so-called front switches, it is required that all manipulations necessary for operation be made at the side of the energy store housing opposite the switching poles and that the energy store housing have the smallest possible dimensions.